Two well known former members of the Provisional IRA have been visited by the PSNI to warn them that their lives are under threat.
Independent.ie can reveal that the pair were told that they should leave the Belfast area "in the short term, immediately".
This follows the brutal daylight murder of a former IRA commander and long-time associate of Gerry Adams yesterday.
The killing of Gerard 'Jock' Davison may have been carried out by dissident republicans, according to senior sources, and has rocked Sinn Fein in the week of the Westminster elections.
Detectives have arrested a 41-year old man in Belfast this morning in connection with the murder.
Detective Chief Inspector Justyn Galloway, who is leading the murder investigation said: "The suspect was detained in Belfast this morning and is being questioned at a police station in the city.”
“A property in north Belfast was searched last night as part of the overall investigation.”
Davison was gunned down in the Markets area of Belfast yesterday, although the PSNI and Sinn Fein were quick to dismiss a terrorist link to the murder.
However, an informed source has told the Irish Independent that "in all probability this was the work of people within the Continuity IRA".
"The speed with which Sinn Fein came out to rule out paramilitary involvement makes perfect sense," said one source.
"The very last thing they need now as the party continues its drive into credible mainstream politics is a feud reupting between the Provisional IRA and a dissident group.
"There has been a feeling for some time in Belfast that the CIRA have been itching to become relevant again, and a high-profile IRA murder gives them that kudos," the source said.
Davison, a prominent figure in the IRA, was gunned down in a gangland-style attack that took place in front of terrified children yesterday.
The leading Republican figure was shot several times by a lone gunman close to his home, in the Markets area of Belfast city centre, around 9am, and died at the scene.
The killing was witnessed by children going to school, one of whom cried out "daddy, daddy".
Local sources claimed the killing of the IRA boss was carried out by people living in the area, which is a staunchly Republican stronghold.
"He was a man who would have made plenty of enemies," a PSNI source said.
The 47-year-old was intrinsically involved in the 2005 killing of Robert McCartney, which seriously jeopardised the peace process. He was accused of drawing his finger across his throat in a gesture to other IRA members in the bar.
He was arrested and questioned about the horrific murder by police but had always denied any involvement. Davison had been jailed in the 1980s for terrorist activities, including an IRA rocket attack on a police patrol when he was a teenager.
He rose through the ranks to become the IRA's commander in Belfast and is also believed to have been on the Army Council.
He later supported Sinn Féin's involvement in the peace process.
Sinn Féin president Gerry Adams described yesterday's shooting as a "brutal act" that should be condemned by all sensible people. "There can be no place today for such actions," he said.
Detective Galloway said: "This was a cold-blooded murder carried out in broad daylight in a residential area and it has no place in the new Northern Ireland."
Asked about a possible threat hanging over Davison, DCI Galloway said: "I do not want to discuss the personal security of any individual, including Mr Davison."
DCI Galloway urged anyone with information to pass it to police, or through the independent charity, Crimestoppers.
"Mr Davison was a father, a grandfather, a brother and a son," he said.
Witnesses said the victim was walking along the street to work at a local community centre when a gunman approached and shot him at point-blank range. Police quickly cordoned off the scene and a yellow forensic tent was placed around the body.
A number of high-profile Belfast republicans were among small groups who watched as scenes-of-crime officers examined the area.
At one stage, distraught family members tried to get to the body and had to be held back.